Example canvas_moire fails on Windows

[myrrlyn]

Platform

Windows 10 x64, build 19631.mn_release-200514-1410

Steps

cd examples/canvas_moire
cargo run --release

Behavior

The window appears, with the orbiting circular patterns, as expected. Upon closing the window, it stops moving, and hangs.

This persists until the terminal program is killed with ^c, at which point the following message appears:

surfman: Could not find the NVIDIA and/or AMD GPU selection symbols. Your application may end up using the wrong GPU (discrete vs. integrated). To fix this issue, ensure that you are using the MSVC version of Rust and invoke the `declare_surfman!()` macro at the root of your crate.
error: process didn't exit successfully: `M:\Projects\Rust\pathfinder\target\release\canvas_moire.exe` (exit code: 0xc000013a, STATUS_CONTROL_C_EXIT)

No backtrace is provided, even with the environment set to request it.

I encountered this error while attempting to pursue the fault described in #344.